Recently, With increasing emphasis on environmental protection, mercury-free light source has become one of important direction of the study. Xenon (Xe) discharging is now the main excited light. Xe radiation may produce a light having a wavelength of 147 nm or 172 nm which can excite luminescent material. To improve energy utilization of the Xe radiation, a suitable luminescent material is necessary to be developed. The suitable luminescent material can effectively absorb the 172 nm light and convert the 172 nm light to a visible light. Now the main commercial luminescent materials are Y2O3:Eu3+, (Y, Gd)BO3:Eu3+ (both of them are red luminescent materials), Zn2SiO4:Mn2+, BaAl12O19:Mn2+ (both of them are green luminescent materials), and BaMgAl10O17:Eu2+ (blue luminescent materials). However, the green luminescent materials, the Zn2SiO4:Mn2+ and the BaAl12O19:Mn2+ both have long afterglow time, which negatively affect the display of dynamic images.
Basically in luminescence mechanism, the luminescent materials emits visible light by absorbing vacuum ultraviolet light (VUV) and then transiting the energy to luminescent ions of the luminescent material which emits light. Accordingly, the luminescent material may have a more effective emitting by improving the absorption of VUV and the energy transition of the material. That is, the sensitized groups contained in the material, such as negative ion groups, can be utilized to sensitize luminescent ions to improve the emitting property. In the negative ion groups, an isolated PO43− group, has a space P—O tetrahedral structure and a strong absorption to the 150 nm-175 nm light. The phosphates, such as Sr3Y(PO4)3, Ca3Y(PO4)3, Ba3La(PO4)3, Ca3La(PO4)3, Sr3La(PO4)3, and Ca3Gd(PO4)3, all contain isolated space P—O tetrahedral structures. These phosphates have excellent stabilities and vacuum ultraviolet radiation resistance. The green luminescent materials having luminescence centers of terbium ions (Tb3+) have been widely used. These Tb3+ contained green luminescent materials, such as Ca5(PO4)3F:Tb3+, Na2GdPO4F2:Tb3+, NaGd(PO3)4:Tb3+, and La(PO3)3:Tb3+, have high luminescence intensity and short fluorescence life time.
However, there are none of disclosure of the luminescent materials, such as, Sr3Y(PO)3, Ca3Y(PO4)3, Ba3La(PO4)3, Ca3La(PO4)3, Sr3La(PO4)3, and Ca3Gd(PO4)3:Tb3+, all of which can be excited by VUV.